A conventional simple fastening device for fastening the equipment and apparatuses described above is disclosed in Japanese Publication of Examined Patent Application [Tokukosho] No. 55-50203.
A conventional simple fasting device uses a bolt to achieve the fastening and thus a tapered hole is formed in a case into which the bolt is inserted, and a plurality of nut segments are provided to slide into the tapered hole. The nut segments engage with and fasten to the bolt. In this case, a spring disposed on the top of each nut segment forces the nut segment in the direction for engaging it with the bolt. An operation ring is provided for releasing the nut segment from the bolt.
The operation ring is disposed in the case in such a way as to be able to turn, and a cam is formed inside of the ring so that a guide pin installed in the nut segment can slide. The surface of the cam is formed in such a way so as to stop the nut segment at the lower limit of fastening to the bolt and at the upper limit of releasing the nut segment from the bolt, so as to limit the movement of the nut segment between those two limits.
In such a simple fastening device, a bolt can be inserted into the case because by inserting the bolt into the case the nut segment rises along the tapered hole against the force of the spring. After inserting the bolt into the case, the force of the spring causes the nut segment to move down so as to face the bolt, so that the nut segment engages with the bolt to be fastened when the case is turned in the fastening direction.
In order to remove the bolt, the operation ring is turned and the cam pin is slid along the cam. With this turning, the nut segment moves from the lower-limit position to the upper-limit position, so as to be released from the bolt.
In order for the bolt to be fastened again, the operation ring is turned in the fastening direction. By this operation, the guide pin slides on the cam surface and the nut segment moves from the upper-limit position to the lower-limit position so as to enter into a standby state for fastening the bolt.
(Patent document) Japanese Publication of Examined Patent Application No. 55-50203
A conventional simple fastening device enables the bolt to be fastened by the one-step operation of inserting the bolt into the case. However, in order to remove the bolt, the operation ring must again be turned in order for the nut segment to move, resulting in troublesome operation to remove the bolt.
Moreover, in order to fasten the bolt, the operation ring must be turned in order for the nut segment to return to the standby state. Accordingly, the operation ring must be turned in order to put the bolt in and out, resulting in troublesome operation and less usability.
Further, a complex cam part must be formed in the operation ring in order for the nut segment to move, so that the structure of the operation ring becomes complex and assembly of the whole device become troublesome.
The problems of the conventional art are solved by the present invention, whose objective is to provide a simple fastening device that (1) enables fastening of an axial member such as a bolt by a one-step operation, (2) has the advantage of releasing the bolt from being fastened without the need for a special operation to put the axial member in and out, and (3) has a simple structure that makes the device easy to assemble.